1. Technical Field
The present invention relates to a gas turbine, and more particularly, to a structure around a bearing of a gas turbine.
This application claims priority to and the benefit of Japanese Patent Application No. 2012-037720 filed on Feb. 23, 2012, the disclosures of which are incorporated by reference herein.
2. Description of the Related Art
A gas turbine includes a compressor, a combustor, and a turbine. The compressor compresses external air to generate compressed air. The combustor mixes a fuel with the compressed air to combust them, generating a combustion gas. The turbine has a rotor rotated by the combustion gas. The rotor generally has a rotor main body and a plurality of blade stages. The rotor main body extends in an axial direction parallel to the rotation axis. The plurality of blade stages is fixed to an outer circumference of the rotor main body to be arranged in the axial direction.
In the above-mentioned gas turbine, with increasing efficiency, a temperature of the combustion gas supplied to the turbine is increased to an extremely high temperature. For this reason, most components of the turbine are parts to be cooled, and a final blade stage of the rotor is also a part to be cooled.
A gas turbine in which a final blade stage is cooled, for example, is disclosed in the following Patent Document 1. A cooling air main passage opened at a downstream end of the rotor main body and extending in the axial direction is formed at the rotor main body of the gas turbine, and a blade cooling air passage configured to introduce cooling air supplied through the cooling air main passage into the final blade stage is formed at the rotor main body. A cooling air pipe not in contact with the rotor main body is disposed at a downstream side of the rotor main body. Compressed air extracted from the compressor via the cooling air pipe is supplied into the cooling air main passage of the rotor main body as cooling air. That is, in the gas turbine, as the compressed air extracted from the compressor is fed to the final blade stage via the cooling air pipe and the rotor main body as the cooling air, the final blade stage is cooled.
Here, in the gas turbine, a downstream side seal retaining ring configured to cover an outer circumferential side of the rotor main body is installed at a downstream side of a bearing configured to rotatably support the rotor main body, and a shaft seal is installed at an inner circumferential side of the downstream side seal retaining ring.
A temperature of the compressed air extracted from the compressor is raised by adiabatic compression in the compressor. The compressed air has a sufficiently low temperature to cool a blade but a relatively high temperature for the bearing of the rotor. For this reason, when the bearing of the rotor is exposed to the compressed air, the bearing may be heated, which causes trouble. Here, in the gas turbine, the shaft seal is disposed at the downstream side of the bearing, and a portion of the compressed air extracted from the compressor is prevented from flowing to the bearing side through a gap between the rotor main body and the cooling air pipe.